fix recognizing the NixOS distribution

Ubuntu is not the only distribution that has a `/etc/lsb-release`,
NixOS has it as well since NixOS/nixpkgs#162168

Author: raboof

rc/trafficserver.in

@@ -56,8 +56,6 @@ elif [ -e /etc/gentoo-release ]; then
     DISTRIB_ID="gentoo"
 elif [ -e /etc/redhat-release ]; then
     DISTRIB_ID="redhat" # also exists on Fedora
-elif [ -e /etc/lsb-release ]; then
-    DISTRIB_ID="ubuntu"
 elif [ -e /etc/debian_version ]; then
     DISTRIB_ID="debian" # also exists on Ubuntu
 elif [ -e /etc/slackware-version ]; then
@@ -68,6 +66,8 @@ elif [ "$UNAME_S" = "FreeBSD" ]; then
     DISTRIB_ID="FreeBSD"
 elif nixos-version > /dev/null; then
     DISTRIB_ID="nixos"
+elif [ -e /etc/lsb-release ]; then
+    DISTRIB_ID="ubuntu"
 fi
 
 # We might want to move over to use /etc/system-release for more distros?